Optical modules

ABSTRACT

An optical module comprising a column-shaped mounting member having a through hole extending along the central axis thereof and having a mounting surface formed by incising a part of the mounting member so as to expose the interior surface of the through hole; and an optical fiber inserted in the through hole and secured in a configuration such that the optical fiber protrudes with a specified length onto the mounting surface. The structure, in which a Bragg diffraction grating is formed in such protruding part of the optical fiber on said mounting surface, can prevent the occurrence of a change in reflective characteristic of the Bragg diffraction grating.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to optical modules.

[0003] 2. Description of the Background Art

[0004] Since Bragg diffraction gratings can selectively reflect thelight of specific wavelengths (hereinafter referred to as “Braggwavelengths”) that satisfy Bragg conditions, they have conventionallybeen employed as wavelength selective filters in optical communicationssystems, for example. Such a Bragg diffraction grating is formed byproviding a periodic refractive index change at an end region of anoptical fiber. The light of the Bragg wavelength determined by theperiodic refractive index change is reflected. An optical fiber withsuch a Bragg diffraction grating formed therein has its one endinstalled and secured to a mounting member such as a ferrule (Refer forexample to Japanese Patent Application Publication No. 2000-353845).

[0005] An optical fiber having a Bragg diffraction grating formedtherein is firmly fixed to a mounting member such as a ferrule byapplying an adhesive between the part of the optical fiber that islocated within the ferrule and the interior walls of the ferrule. Insuch a case, when the optical fiber is secured to the ferrule, suchsecuring causes stress directly on the optical fiber, particularly atthe area where a Bragg diffraction grating has been formed, and suchstress changes the reflective characteristic of the Bragg diffractiongrating.

SUMMARY OF THE INVENTION

[0006] The present invention has been accomplished in light of theabovementioned problem, and it aims to offer optical modules capable ofpreventing such change in the reflective characteristic of a Braggdiffraction grating formed in an optical fiber.

[0007] An optical module of this invention comprises a column-shapedmounting member which has a through hole provided therein extendingalong the central axis thereof and which is partially incised so as toform a mounting surface such that the interior surface of the throughhole is exposed, and an optical fiber which is inserted in the throughhole and secured in a configuration such that the optical fiberprotrudes with a specified length on the mounting surface and a Braggdiffraction grating is formed in such protruding part of the opticalfiber.

[0008] As a result of such arrangement in which the optical fiber isinserted and secured in the through hole of the mounting member suchthat the optical fiber protrudes with a specified length toward themounting surface, the Bragg diffraction grating can be formed in theprotruding part of the optical fiber after the optical fiber is securedto the mounting member. Consequently, it is possible to preventabove-mentioned change that may occur in the reflective characteristicof the Bragg diffraction grating formed in the optical fiber.

[0009] It is preferable that the optical module also include an opticalsemiconductor device installed on the mounting surface and opticallyconnected to an end of the optical fiber. In this case, the structure inwhich the optical semiconductor device is mounted on the mountingsurface of the mounting member allows the downsizing of the opticalmodule.

[0010] It is also desirable that the optical semiconductor device be asemiconductor optical amplifier, as such structure allows a downsizedoptical transmission module to be realized.

[0011] Preferably, the optical semiconductor device is a photodiode.Such structure allows the downsizing of the optical receiver module.

[0012] Furthermore, it is desirable that the mounting surface include afirst area and a second area, the first area having the Braggdiffraction grating region of the optical fiber and a semiconductoroptical receiver device that is optically coupled to an optical devicewhich is capable of reflecting incident light of a specific wavelengthrange while transmitting incident light of another specified wavelengthrange and which is provided between, and optically connected to, theBragg diffraction grating region of the optical fiber and another regionthereof inserted in the through hole, the second area having a lightemitting semiconductor device which is arranged to face an end of theoptical fiber so as to be optically coupled thereto. Such a structurecontributes to realizing a small optical transceiver module.

[0013] Preferably, the mounting member is made of ceramic, which is amaterial thermally stable, excellent in electrical insulation, andapplicable to precise manufacturing.

[0014] It is desirable that the ceramic material be either alumina orzirconia in terms of their high workability and availability.

[0015] It is preferable that the optical module also include a leadframe that can support the mounting member and can electrically beconnected to an optical semiconductor device. With this structure, thelead frame allows the optical module to be installed on a substrateoutside, facilitating the electrical connection between the opticalsemiconductor device and the substrate outside.

[0016] It is also desirable that a resin sealing body also be providedso as to envelop the optical semiconductor device as well as theprotruding part of the optical fiber on the mounting surface. Thisallows the protruding part of the optical fiber and the opticalsemiconductor device on the mounting surface to be preserved inexcellent condition, enabling the individual elements of the opticalmodule to be well protected.

[0017] An optical module according to this invention comprises acolumn-shaped mounting member having a through hole formed therein andextending along the central axis thereof, the mounting member havingbeen partially incised so as to form a mounting surface, exposing theinterior surface of the through hole; and an optical fiber inserted inthe through hole and fixed in an arrangement such that the optical fiberprotrudes with a specified length on the mounting surface, and a Braggdiffraction grating being formed in the protruding part of the opticalfiber after such fixing of the optical fiber.

[0018] In the optical module according to this invention, since theBragg diffraction grating is formed in the protruding part of theoptical fiber protruding toward the mounting surface after the opticalfiber is fixed on the mounting member, it is possible to prevent theoccurrence of a change in the reflective characteristic of the Braggdiffraction grating formed in the optical fiber.

[0019] The optical module of the present invention comprises a mountingmember having a first section, in which a through hole is formed,extending along the central axis thereof, and a second section, in whicha groove is formed in continuation with, and in the same direction as,the through hole; and an optical fiber inserted in the through hole andfixed in a configuration such that the optical fiber protrudes with aspecified length into the groove, the protruding part of the opticalfiber in the groove having a Bragg diffraction grating formed therein.

[0020] In the optical module according to this invention, since anoptical fiber is inserted in the through hole formed in the firstsection of the mounting member and fixed in a configuration such thatthe optical fiber protrudes with a specified length into the grooveformed in the second section of the mounting member, the Braggdiffraction grating can be formed in the optical fiber that protrudes inthe groove. With this structure, it is possible to prevent theoccurrence of a change in the reflective characteristic of the Braggdiffraction grating formed in the optical fiber.

[0021] The optical module of the present invention comprises a mountingmember having a first section wherein a through hole is formed extendingalong the central axis thereof, and a second section wherein a groove isformed extending in continuation with, and in the same direction as, thethrough hole; and an optical fiber inserted in the through hole andsecured in a configuration such that the optical fiber protrudes with aspecified length into the groove, the protruding part of the opticalfiber in the groove having a Bragg diffraction grating formed after suchsecuring of the optical fiber.

[0022] In the optical module according to this invention, since theBragg diffraction grating is formed in the protruding part of theoptical fiber in the groove after the optical fiber is secured on themounting member, it is possible to prevent the occurrence of a change inthe reflective characteristic of the Bragg diffraction grating formed inthe optical fiber.

[0023] According to the present invention, as described in detailheretofore, it is possible to offer an optical module in which theoccurrence of a change in the reflective characteristic of a Braggdiffraction grating formed in an optical fiber can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 is a sectional view of an optical transmission moduleaccording to a first embodiment of the present invention.

[0025]FIG. 2 is a plan view of the optical transmission module shown inFIG. 1.

[0026]FIG. 3 is a perspective view of the exterior structure of theoptical transmission module of FIG. 1.

[0027]FIG. 4 is a perspective view of the exterior structure of amodification to the optical transmission module of the first embodimentof this invention.

[0028]FIG. 5 is a sectional view of an optical receiver module accordingto a second embodiment of the present invention.

[0029]FIG. 6 is a plan view of the optical receiver module illustratedin FIG. 5.

[0030]FIG. 7 is a perspective view of the exterior structure of theoptical receiver module shown in FIG. 5.

[0031]FIG. 8 is a perspective view of the exterior structure of amodification to the optical receiver module of the second embodiment ofthis invention.

[0032]FIG. 9 is a sectional view of an optical transceiver moduleaccording to a third embodiment of the present invention.

[0033]FIG. 10 is a plan view of the optical transceiver moduleillustrated in FIG. 9.

[0034]FIG. 11 is a front view of the optical transceiver moduleillustrated in FIG. 9.

[0035]FIG. 12 is a perspective view of the exterior structure of theoptical transceiver module shown in FIG. 9.

[0036]FIG. 13 is a perspective view of the exterior structure of theoptical transceiver module of FIG. 9, when its resin sealing isexcluded.

DETAILED DESCRIPTION OF THE INVENTION

[0037] Preferred embodiments for carrying out the present invention aredescribed hereinafter with reference to the accompanying drawings. Inthe drawings, the same components are denoted by the same referencenumerals, and redundant descriptions thereof are omitted.

[0038] The First Embodiment

[0039] In the first embodiment, the present invention has been appliedto an optical transmission module capable of converting input electricalsignals into optical signals for transmission. FIG. 1 is a sectionalview of the optical transmission module according to the firstembodiment, while FIG. 2 is a plan view thereof. FIG. 3 is a perspectiveview of the exterior structure of the optical transmission module shownin FIG. 1.

[0040] Referring to FIGS. 1 to 3, the optical transmission module OM1includes a ferrule 1 as an embodiment of a mounting member, an opticalfiber 3, a semiconductor optical amplifier 5 as an embodiment of anoptical semiconductor device, and other parts.

[0041] The ferrule 1 is a column-shaped member (a cylindrical member inthe first embodiment) made of ceramics (either alumina or zirconia forthis embodiment) and has a through hole 7 extending along the centralaxis thereof. The through hole 7 is formed with an accuracy ofapproximately ±2 μm relative to the central axis of the ferrule 1. Atone end of the ferrule 1, a mounting surface 9 is formed in parallelwith the central axis of the ferrule 1. The mounting surface 9 can beformed in a method such as polishing or electric discharge machining.The mounting surface 9 is formed incising the through hole 7 at aspecific distance from the central axis of the ferrule 1, for example,at a distance of approximately 10 μm with an accuracy of within about ±5μm. As a result of these processing, the ferrule 1 have a first section1 a in which a through hole 7 is formed, and a second section 1 b inwhich a groove 11 is formed extending in continuation with, and in thesame direction as, the through hole 7.

[0042] For example, it is possible to design the ferrule 1 to have adiameter in the range of 1.25 mm to 2.50 mm and a length in the range of5 mm to 15 mm along the central axis thereof. The through hole 7 can bedesigned to have a diameter of 126 μm±2 μm, and the mounting surface 9can be designed to have a length in the range of 3 to 15 mm in thedirection along the central axis thereof.

[0043] The optical fiber 3 is inserted in the through hole 7 of theferrule 1 so as to protrude with a specified length (for example, from 2to 5 mm) toward the mounting surface, and fixed with an adhesive or byother means to the ferrule 1. In other words, the optical fiber 3 isinserted in and secured to the through hole 7 in a configuration suchthat the optical fiber 3 protrudes with a specified length in the groove11.

[0044] A Bragg diffraction grating 13 is provided in the optical fiber 3at the exposed part thereof that protrudes onto the mounting surface 9,or in other words, into the groove 11. The Bragg diffraction grating 13is formed after securing the optical fiber 3 to the ferrule 1. Asfurther described herein later, the Bragg diffraction grating 13composes an optical cavity, in combination with a light reflectingsurface 5 b of the semiconductor optical amplifier 5 in the opticaltransmission module OM1. In a typical case, the Bragg diffractiongrating 13 can be designed to have a pitch of approximately 0.46 μm anda total length of 2 to 3.0 mm. With such a pitch, the reflectionwavelength of the Bragg diffraction grating is, for example, in awavelength band such as the 1310 nm band.

[0045] In a commonly employed method of producing the Bragg diffractiongrating 13, germanium dioxide (GeO₂) is added in advance as aphotosensitivity enhancement agent to the core or the clad of the silica(SiO₂) based optical fiber, and subsequently the optical fiber isirradiated by light of a specified wavelength, such as ultraviolet rays,so that a modulating pattern of the reflective index is formedcorresponding to the distribution of the light energy intensity.Specifically, the specific modulation pattern of the reflective index isprovided in at least either of the core or clad of the optical fiber byirradiating ultraviolet rays of a specified wavelength through a maskfrom a source such as a laser.

[0046] The semiconductor optical amplifier 5 is arranged on the mountingsurface 9 of the ferrule 1 in a configuration such that the lightemitting surface 5 a of the semiconductor optical amplifier 5 faces anend of the optical fiber 3 so as to be optically coupled to the end ofthe optical fiber 3. The semiconductor optical amplifier 5 can be asemiconductor optical amplifier chip having a double hetero structure ofInGsAsP and InP, for example. The semiconductor optical amplifier 5 canbe installed on the mounting surface 9, for example, in a manner suchthat it is mounted on a metallized layer (a metallized pattern) formedon the mounting surface 9.

[0047] While one side of the semiconductor optical amplifier 5constitutes a light emitting surface 5 a, the other side thereof forms alight reflecting surface 5 b. The light reflecting surface 5 b has acoating thereon, whose reflective index ranges from 85 to 100%.

[0048] The optical transmission module OM1 functions as describedhereinafter. When electric current containing specified signals isdelivered to the semiconductor optical amplifier 5, light is releasedfrom the light emitting surface 5 a thereof. The light passes throughone end surface of the optical fiber 3, and enters into the opticalfiber 3. Thereafter, laser oscillation occurs between the Braggdiffraction grating 13 and the light reflecting surface 5 b of thesemiconductor optical amplifier 5, thereby generating laser light. Thelaser light passes through the optical fiber 3 and is output from theother end thereof.

[0049] It is ideal to design a groove 11 formed on the mounting surface9 of the ferrule 1 to have a depth such that the center of the lightemitting part of the semiconductor optical amplifier 5 installed on andsecured to the mounting surface 9 is positioned on the central axis ofthe through hole 7, that is, on the central axis of the optical fiber 3.By doing so, the light emitted from the semiconductor optical amplifier5 can be effectively led into the optical fiber 3.

[0050] As described heretofore, the optical transmission module OM1according to the first embodiment of the present invention has theoptical fiber 3 inserted in the through hole 7 of the ferrule 1 andsecured in a configuration such that the optical fiber 3 protrudes witha specified length toward the mounting surface 9 of the ferrule 1. Withthis structure, the Bragg diffraction grating 13 can be produced easilyin such protruding part of the optical fiber 3 after the optical fiber 3has been secured to the ferrule 1. Consequently, the occurrence of achange in the reflective characteristic of the Bragg diffraction grating13 formed in the optical fiber 3 can be prevented.

[0051] The optical transmission module OM1 according to the firstembodiment of the present invention includes the semiconductor opticalamplifier 5 installed on the mounting surface 9 of the ferrule 1,allowing the downsizing of the optical transmission module OM1.

[0052] In the optical transmission module OM1 of the first embodiment,the ferrule 1 consists of a ceramic material, which is thermally stable,excellent in electric insulation and applicable to precisemanufacturing. The ceramic material preferably is selected from eitheralumina or zirconia, as this will ensure excellent workability andavailability.

[0053] In a modification to the first embodiment, as shown in FIG. 4, anoptical fiber having a pig tail portion15 can be employed as the opticalfiber 3 of the optical transmission module OM1.

[0054] The Second Embodiment

[0055] In a second embodiment, the present invention has been applied toan optical receiver module that is capable of converting input opticalsignals to electrical signals for reception. FIG. 5 illustrates a crosssection of the optical receiver module according to the secondembodiment of the present invention. FIG. 6 is a plan view of theoptical receiver module illustrated in FIG. 5. FIG. 7 shows aperspective view of the exterior structure of the optical receivermodule OM2 of FIG. 5.

[0056] Referring to FIGS. 5 to 7, the optical receiver module OM2includes a ferrule 1, an optical fiber 3, a photodiode 21 as anembodiment of optical semiconductor device, and other parts.

[0057] The photodiode 21 is placed on the mounting surface 9 of theferrule 1 in a configuration such that the light incident surface 21 aof the photodiode 21 faces an end of the optical fiber 3 so as to beoptically coupled to the end of the optical fiber 3. An end-illuminatedtype photodiode containing InGaAsP for a light-receiving part can beemployed as the photodiode 21, for example. The photodiode 21 can beinstalled on the mounting surface 9, for example, on a metallized layerformed thereon.

[0058] As described heretofore, also in the optical receiver module OM2according to the second embodiment of the present invention, the opticalfiber 3 is inserted in the through hole 7 of the ferrule 1 and securedin a configuration such that the optical fiber 3 protrudes with aspecified length toward the mounting surface 9 of the ferrule 1. Withthis structure, the Bragg diffraction grating 13 can be produced easilyin the protruding part of the optical fiber 3 on the mounting surface 9after the optical fiber 3 has been secured to the ferrule 1.Consequently, it is possible to prevent the occurrence of a change inthe reflective characteristic of the Bragg diffraction grating 13 formedin the optical fiber 3.

[0059] In the optical receiver module OM2 according to the secondembodiment of the present invention, the photodiode 21 is installed onthe mounting surface 9 of the ferrule 1. This configuration contributesto realizing the downsized optical receiver module OM2.

[0060] In a modification to the second embodiment, as illustrated inFIG. 8, an optical fiber having a pig tail portion 15 can be employed asthe optical fiber 3 of the optical receiver module OM2.

[0061] The Third Embodiment

[0062] In a third embodiment, the present invention is applied to anoptical transceiver module OM3 that is capable both of converting inputelectrical signals to optical signals for transmission and of changinginput optical signals into electric signals for reception. FIG. 9 is across section view of the optical transceiver module OM3 according tothe third embodiment, while FIG. 10 shows a plan view thereof. FIG. 11is a front view of the optical transceiver module illustrated in FIG. 9and FIG. 12 shows a perspective view of its exterior structure. FIG. 13illustrates the optical transceiver module of FIG. 9 in a state whereits resin sealing body is excluded.

[0063] Referring to FIGS. 9 to 12, the optical transceiver module OM3includes a ferrule 1, an optical fiber 3, a semiconductor opticalamplifier 5 as an embodiment of a semiconductor light emitting device, aphotodiode 31 as an embodiment of a semiconductor optical receiverdevice, an optical device 33, and other parts.

[0064] The ferrule 1 has a mounting surface 9 consisting of a first area9 a and a second area 9 b, both of which are arranged to extend in thesame direction as a groove 11. The part where a Bragg diffractiongrating 13 is formed in the optical fiber 3 lies in the first section 9a.

[0065] The semiconductor optical amplifier 5 is provided on the secondarea 9 b of the mounting surface 9 of the ferrule 1 in a configurationsuch that the light emitting surface 5 a of the semiconductor opticalamplifier 5 faces an end of the optical fiber 3 so as to be opticallycoupled to the end of the optical fiber 3.

[0066] The optical device 33 is capable of reflecting the incident lightof a first wavelength range (for example, a 1550 nm wavelength band)while transmitting the incident light of a second wavelength range (forexample, a 1310 nm band). An optical filter incorporating a dielectricmultilayer film can be employed as the optical device 33. The opticaldevice 33 is placed between a part 3 b of the optical fiber 3 in thefirst area 9 a, in which part the Bragg diffraction grating 13 is formedand a part 3 a of the optical fiber 3, which part is inserted in thethrough hole 7, and the optical device 33 is optically connected to bothof the parts 3 a and 3 b. The optical device 33 forms an acute angle(for example, at approximately 30°) relative to the mounting surface 9of the ferrule 1.

[0067] The optical device 33 is capable of transmitting the laser lightof the second wavelength range that has been generated by laseroscillation between the Bragg diffraction grating 13 formed in theoptical fiber 3 and the light reflecting surface 5 b of thesemiconductor optical amplifier 5. On the other hand, the optical device33 can reflect such light of the first wavelength range that propagatesthrough the optical fiber 3 in the opposite direction relative to theaforementioned laser light.

[0068] The photodiode 31 is provided in the first area 9 a of themounting surface 9 and optically connected to the optical device 33. Arear-illuminated type photodiode can be employed as the photodiode 31.The photodiode 31 is placed on a mounting member 35 and positioned abovethe optical fiber 3. In other words, the optical fiber 3 is positionedbetween the photodiode 31 and the ferrule 1. The mounting member 35 canbe used as a fixing member to secure the optical fiber 3. The photodiode31 receives the light of the first wavelength range that is incident viathe optical fiber 3 (the part 3 a inserted in the through hole 7), theoptical device 33, and the mounting member 35.

[0069] The mounting member 35 can transmit the light of the firstwavelength range therethrough and has the mounting surface 35 a forplacing the photodiode 31 thereon. The rear side of the mounting surface35 a functions as the basis for determining the location of the opticalfiber 3. The photodiode 31 is provided in an arrangement such that thelight incident surface thereof faces the mounting surface 35 a.

[0070] The optical transceiver module OM3 also contains a lead frame 37.The lead frame 37 includes supporting parts 37 a, which are in contactwith the exterior surface of the ferrule 1 so as to support the ferrule1; terminals 37 b and 37 c electrically connected to the semiconductoroptical amplifier 5; and terminals 37 d and 37 e electrically connectedto the photodiode 31.

[0071] The semiconductor optical amplifier 5 incorporates an anode and acathode. The anode is connected to the terminal 37 b via a connectingmember 39 a such as a bonding wire, and similarly the cathode isconnected to the terminal 37 c via a connecting member 39 b such as abonding wire. The photodiode 31 also includes an anode and a cathode.The anode is connected to the terminal 37 d via a connecting member 39 csuch as a bonding wire, and similarly the cathode is connected to theterminal 37 e via a connecting member 39 d such as a bonding wire.

[0072] The optical transceiver module OM3 incorporates a resin sealingbody 41 to envelop the protruding part of the optical fiber 3 on themounting surface 9, the semiconductor optical amplifier 5, thephotodiode 31, and the optical device 33. Along with the protection ofthe individual parts, this structure enables the protruding part of theoptical fiber 3 on the mounting surface 9, the semiconductor opticalamplifier 5, the photodiode 31, and the optical device 33 to bemaintained in excellent conditions. It is preferable that the resinsealing body 41 be transparent such that the light of both the first andsecond wavelength ranges are transmittable in order to ensure therespective optical connections between the semiconductor opticalamplifier 5 and the optical fiber 3, between the optical device 33 andthe optical fiber 3 (3 a, 3 b), and between the optical device 33 andthe photodiode 31.

[0073] As described heretofore, also in the optical transceiver moduleOM3 of the third embodiment, the optical fiber 3 is inserted in thethrough hole 7 of the ferrule 1 and secured in a configuration such thatthe optical fiber 3 protrudes with a specified length toward themounting surface 9 of the ferrule 1. As described heretofore, also inthe optical transceiver module OM3 of the third embodiment, the opticalfiber 3 is inserted in the through hole 7 of the ferrule 1 and securedin a configuration such that the optical fiber 3 protrudes with aspecified length toward the mounting surface 9 of the ferrule 1. Withthis structure, the Bragg diffraction grating 13 can be produced easilyin the protruding part of the optical fiber 3 on the mounting surface 9after the optical fiber 3 is secured to the ferrule 1. Consequently, itis possible to prevent the occurrence of a change in the reflectivecharacteristic of the Bragg diffraction grating 13 formed in the opticalfiber 3.

[0074] In the optical transceiver module OM3 of the third embodiment,the semiconductor optical amplifier 5 and the photodiode 31 areinstalled on the mounting surface 9 of the ferrule 1. This contributesto downsizing the optical transceiver module OM3.

[0075] The optical transceiver module OM3 of the third embodiment alsocontains a lead frame 37, which supports the ferrule 1 and iselectrically connected to optical semiconductor devices including thesemiconductor optical amplifier 5 and the photodiode 31. The lead frame37 allows the optical transceiver module OM3 to be installed on asubstrate outside (not indicated in Figures), and also facilitates theelectrical connection between the optical semiconductor devices (thesemiconductor optical amplifier 5 and the photodiode 31) and thesubstrate outside.

[0076] The optical modules according to the present invention are notlimited to the embodiments herein provided, and various othermodifications thereof can be made. For example, devices other than thephotodiode 21 and 31 can be employed as the optical receiver device thatis capable of converting optical signals to electric signals. Likewise,devices other than the semiconductor optical amplifier 5 can be used asthe optical transmission device for converting electric signals tooptical signals. The optical transmission module OM1 of the firstembodiment as well as the optical receiver module OM2 of the secondembodiment may incorporate a lead frame 37 and a resin sealing body 41.In the optical transceiver module OM3 of the third embodiment, anoptical fiber having a pig tail portion can be employed as the opticalfiber 3.

What is claimed is:
 1. An optical module comprising: a column-shapedmounting member having a through hole extending in the direction of thecentral axis thereof and having a mounting surface formed by partiallyincising a part of said mounting member so as to expose the interiorsurface of said through hole; and an optical fiber inserted in saidthrough hole and secured in a configuration such that said optical fiberprotrudes with a specified length onto said mounting surface, a Braggdiffraction grating being formed in such protruding part of said opticalfiber on said mounting surface.
 2. An optical module as defined in claim1, further comprising an optical semiconductor device provided on saidmounting surface and optically connected to an end of said opticalfiber.
 3. An optical module as defined in claim 2, wherein said opticalsemiconductor device is a semiconductor optical amplifier.
 4. An opticalmodule as defined in claim 2, wherein said optical semiconductor deviceis a photodiode.
 5. An optical module as defined in claim 1, whereinsaid mounting surface includes a first area and a second area, bothbeing arranged so as to extend in the same direction as a groove that isformed extending in continuation with, and in the same direction as,said through hole; said protruding part where said Bragg diffractiongrating is formed in said optical fiber is located in said first area;and wherein said optical module further comprises: a semiconductor lightemitting device provided in said second area of said mounting surface soas to face an end of said optical fiber and optically connected to saidend of said optical fiber; an optical device capable of reflectingincident light of a specified wavelength range and transmitting light ofanother specified wavelength range, said optical device being positionedbetween the part of said optical fiber where said Bragg diffractiongrating is formed and the part of said optical fiber which is insertedin said through hole so that said optical device is optically connectedto both of said parts of said optical fiber; and a semiconductor opticalreceiver device provided in said first area of said mounting surface andoptically connected to said optical device.
 6. An optical module asdefined in claim 1, wherein said mounting member is made of a ceramicmaterial.
 7. An optical module as defined in claim 6, wherein saidceramic material is either alumina or zirconia.
 8. An optical module asdefined in claim 1, wherein a lead frame is also provided so as tosupport said mounting member, said lead frame being electricallyconnected to said optical semiconductor device.
 9. An optical module asdefined in claim 1, wherein a resin sealing body is also provided toenvelope said optical semiconductor device and said protruding part ofsaid optical fiber on said mounting surface.
 10. An optical modulecomprising: a column-shaped mounting member having a through holeextending in the direction of the central axis thereof and having amounting surface formed by partially incising a part of said mountingmember so as to expose the interior surface of said through hole; and anoptical fiber inserted in said through hole and secured in aconfiguration such that said optical fiber protrudes with a specifiedlength onto said mounting surface, a Bragg diffraction grating beingformed in such protruding part of said optical fiber on said mountingsurface after such securing of said optical fiber.
 11. An optical modulecomprising: a mounting member having a first section wherein a throughhole is formed extending along the central axis thereof, and a secondsection wherein a groove is formed extending in continuation with, andin the same direction as, said through hole; and an optical fiberinserted in said through hole and secured in a configuration such thatsaid optical fiber protrudes with a specified length into said groove, aBragg diffraction grating being formed in such protruding part of saidoptical fiber.
 12. An optical module comprising: a mounting memberhaving a first section wherein a through hole is formed extending alongthe central axis thereof, and a second section wherein a groove isformed extending in continuation with, and in the same direction as,said through hole; and an optical fiber inserted in said through holeand secured in a configuration such that said optical fiber protrudeswith a specified length into said groove, a Bragg diffraction gratingbeing formed in such protruding part of said optical fiber after suchsecuring of said optical fiber.